A necessary condition for the flight of unmanned air vehicles (UAVs) on civil flight paths is that they have an equivalent level of safety (ELOS) to that of conventional manned vehicles, in other words that they have collision avoidance systems which can reduce the risk of air-to-air collisions to an equivalent level to that which is found for manned air vehicles.
The access of unmanned air vehicles to non-segregated airspaces is dependent not only on their capacity to detect the presence of an airborne object and manoeuvre autonomously to avoid it, but also on their capacity to interpret data relating to the airspace in which they are located, as a pilot would, in other words to surveil any airborne objects present and to predict sufficiently far in advance any points of impact to be avoided.
Collision prediction systems and methods are known, for example, from EP 1 630 766 (Saab) or WO 2008020889 (Boeing). However, these systems are limited both as to the type of prediction which they can provide, since they make only a short-term prediction, and as to the operating modes which they use to make this prediction.